[PATCH v2 02/12] KVM: pfncache: add a mark-dirty helper

[Paul Durrant <paul@xen.org>]

From: Paul Durrant <pdurrant@amazon.com>

At the moment pages are marked dirty by open-coded calls to
mark_page_dirty_in_slot(), directly deferefencing the gpa and memslot
from the cache. After a subsequent patch these may not always be set
so add a helper now so that caller will protected from the need to know
about this detail.

NOTE: Pages are now marked dirty while the cache lock is held. This is
      to ensure that gpa and memslot are mutually consistent.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw2@infradead.org>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
---
 arch/x86/kvm/x86.c       |  2 +-
 arch/x86/kvm/xen.c       | 13 ++++++-------
 include/linux/kvm_host.h |  7 +++++++
 virt/kvm/pfncache.c      |  6 ++++++
 4 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6c9c81e82e65..d669a8801265 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3137,7 +3137,7 @@ static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
 
 	guest_hv_clock->version = ++vcpu->hv_clock.version;
 
-	mark_page_dirty_in_slot(v->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
+	kvm_gpc_mark_dirty(gpc);
 	read_unlock_irqrestore(&gpc->lock, flags);
 
 	trace_kvm_pvclock_update(v->vcpu_id, &vcpu->hv_clock);
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 40edf4d1974c..33fddd29824b 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -430,14 +430,13 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 		smp_wmb();
 	}
 
-	if (user_len2)
+	if (user_len2) {
+		kvm_gpc_mark_dirty(gpc2);
 		read_unlock(&gpc2->lock);
+	}
 
+	kvm_gpc_mark_dirty(gpc1);
 	read_unlock_irqrestore(&gpc1->lock, flags);
-
-	mark_page_dirty_in_slot(v->kvm, gpc1->memslot, gpc1->gpa >> PAGE_SHIFT);
-	if (user_len2)
-		mark_page_dirty_in_slot(v->kvm, gpc2->memslot, gpc2->gpa >> PAGE_SHIFT);
 }
 
 void kvm_xen_update_runstate(struct kvm_vcpu *v, int state)
@@ -543,13 +542,13 @@ void kvm_xen_inject_pending_events(struct kvm_vcpu *v)
 			     : "0" (evtchn_pending_sel32));
 		WRITE_ONCE(vi->evtchn_upcall_pending, 1);
 	}
+
+	kvm_gpc_mark_dirty(gpc);
 	read_unlock_irqrestore(&gpc->lock, flags);
 
 	/* For the per-vCPU lapic vector, deliver it as MSI. */
 	if (v->arch.xen.upcall_vector)
 		kvm_xen_inject_vcpu_vector(v);
-
-	mark_page_dirty_in_slot(v->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
 }
 
 int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fb6c6109fdca..c71e8fbccaaf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1367,6 +1367,13 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
  */
 void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
 
+/**
+ * kvm_gpc_mark_dirty - mark a cached page as dirty.
+ *
+ * @gpc:	   struct gfn_to_pfn_cache object.
+ */
+void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc);
+
 void kvm_sigset_activate(struct kvm_vcpu *vcpu);
 void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
 
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 0f36acdf577f..b68ed7fa56a2 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -386,6 +386,12 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_activate);
 
+void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
+{
+	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
+}
+EXPORT_SYMBOL_GPL(kvm_gpc_mark_dirty);
+
 void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)
 {
 	struct kvm *kvm = gpc->kvm;
-- 
2.39.2